1. Field of the Invention
The present invention relates to a guard that helps prevent a turbine of an engine turbocharger from violently exiting the downpipe during a catastrophic turbocharger failure.
2. Background of the Prior Art
A turbocharger is a forced induction device that forces more air and fuel into the combustion chamber of an internal combustion engine than can be achieved if atmospheric pressure alone is used for air-fuel introduction into the engine in the case of a naturally aspirated engine. This increase in air-fuel density entering into the combustion change increases the volumetric efficiency of the engine, which increases the overall performance of the engine in the form of a horsepower output increase.
Unlike a supercharger, which is mechanically tied to the engine itself, the turbocharger does not depend on power from the engine for its operation. The turbocharger uses the kinetic energy from the engine's exhaust gases to drive a compressor that compresses the ambient air prior to the air entering the intake manifold in order to increase the overall mass of air and fuel entering the combustion chamber of the engine. With an increase of air mass within the combustion chamber, the volumetric efficiency of the engine is increased so that the output power of the engine is also increased. Alternately, the turbocharger system can be designed to increase the fuel efficiency of the vehicle in which the device is installed without increasing the engine's power output.
At the heart of the turbocharger's compressor is the turbine which captures the kinetic energy of the exhaust gases that drive the compressor assembly. The turbine faces the downpipe of the exhaust system and spins at rates of up to about 250,000 RPM and can reach temperatures of about 1,500 degrees Fahrenheit.
When a turbocharger is installed in a passenger vehicle and the turbine fails, the typical net result is an unhappy vehicle owner and a happy mechanic as such failures tend to be costly to repair. However, when the turbocharger is installed on a performance vehicle, such as a competition drag racing vehicle, a turbine failure can be substantially more dramatic. In such extreme environments, a turbine failure often results from the turbine shaft failure which causes the turbine to separate from the rest of the compressor. The separated turbine, spinning at transonic speeds and white hot, shoots into the downpipe of the exhaust system to which the turbocharger is installed. At this point the turbine may shoot through the wall of the elbow of the downpipe and pass through the relatively thin firewall of the engine compartment and into the passenger compartment of the vehicle, and possibly directly into the torso of the driver on the opposing side of the firewall, resulting in serious injury or death. Alternately, if the downpipe is sufficiently strong, the turbine travels down the length of the downpipe and exits the vehicle through the exhaust system with the exhaust gases produced. Typically, in order to increase the aesthetic appeal of the competition vehicle, the outlet of the exhaust system may be facing straight upward or may be a side exit. In either case, the turbine, still white hot and weighing several pounds, shoots out of the exhaust outlet at speeds that may be in excess of 100 MPH. If the turbine hits a person, such as a spectator or even a pit crew member if the exhaust system outlet points rearwardly of the vehicle, serious injury or death can occur.
In order to address this potentially deadly problem, and prodded by the rules implemented at many competition venues, many competition vehicle owners install a shield within the downpipe in order to reduce the risk of injury from a broken off turbine of a turbocharger compressor. As seen in FIG. 1, such a shield involves passing a pair of bolts, oriented approximately normal and in close proximity to one another, through the downpipe in a cross pattern. As the turbine engages the bolts, the turbine is either outright stopped or is shattered into smaller fragments, which individually do not have the energy to penetrate the downpipe and firewall or do not have sufficient mass to travel very far when shot out of the outlet of the exhaust system, thereby reducing the potential for injury. While such shielding does reduce injury potential, this type of system is not without its drawbacks.
One shortcoming of this shielding system lies in the fact that many mechanics pass the bolts through corresponding openings made in the downpipe and simply place a nut on the distal end of the bolts in order to secure the bolts thereat, foregoing the more substantial welding process. Such nuts, even if they are lock nuts, can come loose and separate from the bolt, allowing the bolt to separate from the downpipe, due to the extreme vibrations that occur at this part of the engine. In the hectic day of racing, a mechanic may not notice the loss of the bolts, and their attendant shielding capability, during routine inspections of the engine between races.
Another problem with these bolt shields lies in the fact that many mechanics simply use any bolt that can be found to place into the downpipe. While a steel bolt found at a home center supply house may be more than capable of holding a deck board to a joist, the same bolt may quickly shear off when violently interacted with a high speed turbine, thereby not only not resolving the initial problem, but also introducing a pair of bolt fragments into the potentially deadly projectile mix exiting the exhaust system of the vehicle.
Yet another problem lies in the fact that due to size limitations, many mechanics install such bolts on the distal side of the elbow of the downpipe so that the turbine does not encounter the shield until after passing through the elbow of the downpipe. While the shield may protect spectators at the racing event from harm, the turbine can still pass through the downpipe and the firewall and enter the passenger compartment of the vehicle before ever encountering the shield.
What is needed is a shield that either stops an escaped turbocharger turbine or at least substantially reduces the potential danger posed by such a turbine, which shield addresses the above mentioned shortcomings found in the art. Specifically, such a shield must be able to stay in place during the racing day irrespective of the environment in which the shield is installed. Such a device must have sufficient material strength so as to be able to properly assert itself against the extreme violence occasioned onto the shield by a high speed high temperature turbine. Such a device must be designed so that it is installed within the turbo exhaust system at a location whereat both spectators and vehicle passengers are protected by the device irrespective of any size constrains introduced by the downpipe.